Pulse sequencing system

ABSTRACT

It is herein disclosed a system for providing a cyclical sequence of equally spaced operation controlling pulses to elements or devices comprising a plurality of element banks. The number of banks of elements and the number of elements per bank may be varied easily within a given cycle duration and yet remain equally spaced in time regardless of the number of elements per bank. Further, the desired sequencing may be carried on in a forward or reverse direction. The above is carried out by providing a sufficient number of element operation controlling pulses to allow the selection among such pulses such that any number of elements per bank may be chosen for a predetermined operation up to a predetermined maximum number such that they are equally spaced in time. Bank signals are provided which are then gated by the element controlling pulses. The aforesaid is carried out by a bank selector matrix which comprises a plurality of terminals, from which selected terminals are connected to receive bank signals and the desired element pulses and also to appropriate gating means. The output from the gating means then comprises a cyclical sequence of pulses equally spaced in time which may be sent to those groups of elements located in banks for which bank signals have been provided.

Wavre [4 1 Apr. 4, 1972 [541 PULSE SEQUENCING SYSTEM [72] Inventor: Andre Wavre, Monroeville, Pa.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

22 Filed: Feb. 13, 1969 21 Appl.No.: 798,913

[52] US. Cl ..340/l68, 176/22 [51] Int. Cl. ..H( )4q [58] Field ol'Search ..340/l68, 147 GR, 147 MD;

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 226,843 9/1958 Australia ..204/l93.3

Primary Examiner-Eugene G. Botz An0rney-A. T. Stratton, Z. L. Dermer and J. William Wigert, Jr.

PULSE GENERATOR DECODER REVERSIBLE COUNTER [5 7] ABSTRACT It is herein disclosed a system for providing a cyclical sequence of equally spaced operation controlling pulses to elements or devices comprising a plurality of element banks. The number of banks of elements and the number of elements per bank may be varied easily within a given cycle duration and yet remain equally spaced in time regardless of the number of elements per bank. Further, the desired sequencing may be carried on in a forward or reverse direction. The above is carried out by providing a sufficient number of element operation controlling pulses to allow the selection among such pulses such that any number of elements per bank may be chosen for a predetermined operation up to a predetermined maximum number such that they are equally spaced in time. Bank signals are provided which are then gated by the element controlling pulses. The aforesaid is carried out by a bank selector matrix which comprises a plurality of terminals, from which selected terminals are connected to receive bank signals and the desired element pulses and also to appropriate gating means. The output from the gating means then comprises a cyclical sequence of pulses equally spaced in time which may be sent to those groups of elements located in banks for which bank signals have been provided.

6 Claims, 4 Drawing Figures lBI AJ R/ WJ y? SHUTDOWN BANKS SHEET 3 OF 3 CONTROL PATENTEDAPR 4 I972 ELEMENT PULSES 3RD GROUP: BANK Cl OR C3 OR SI IST GROUP: BANK C2 OR C4 OR 52 2ND GROUP; BANK C2 OR C4 OR 82 3 RD GROUP: BANK C2 OR C4OR S2 F IG. 4

PULSE SEQUENCING SYSTEM CROSS REFERENCES TO RELATED APPLICATIONS The present invention is related to the invention covered by copending patent application (Westinghouse case No. 40,534), Ser. No. 798,911, filing date Feb. 13, 1969, entitled Power Regulation System by Andre Wavre and Francis Thompson; copending application (Westinghouse case No. 40,535), Ser. No. 798,912, filing date Feb. 13, 1969, entitled Power Multiplexing System by Andre Wavre; and copending patent application (Westinghouse case No. 40,741), Ser. No. 798,914, filing date Feb. 13, 1969, entitled Signal Sequencing System, by Andre Wavre and Dean Santis; all of which are assigned to the assignee of the present invention and filed concurrently herewith.

BACKGROUND OF THE INVENTION The present invention relates to a system for sequencing elements located in a plurality of banks and wherein the number of banks may vary and the number of elements per bank may vary in number from one to N elements.

Cyclically providing pulses to a varying number of elements located in a plurality of banks is required in an electrical system, such as, for example, a nuclear reactor rod control system. In a nuclear rod control system, control rods are arranged in banks comprising up to several groups of control rods per bank. When it is desired to increase or decrease the energy output of the nuclear reactor, it is necessary to insert or withdraw the control rods in a systematic and determinable fashion. To withdraw, for example, the first bank of control rods it is necessary to sequentially withdraw each group within the bank of control rods one increment and then repeat the sequence as many times as necessary until the sum of the incremental changes reaches the desired withdrawal distance. Thus, if the bank comprises three groups of control rods it is necessary to first withdraw the first group one increment, then the second group one increment, and finally the third group one increment. If it is desired to continue to increase the energy output of the nuclear reactor the bank would be cycled again such that the first group would be withdrawn one increment, followed by'the second and the third, and so forth. At the same or different times other banks of elements may also be withdrawn in an identical manner.

Several requirements must be met in such a system. The groups of control rods within each bank must be withdrawn such that they are spaced equally within each cycle. However, the number of groups per bank in a nuclear reactor is determined by many factors including the output requirements of the plant, the nuclear properties of the plant, and so forth. Desirably then, a rod control system must meet the further requirement that the groups of control rods be withdrawn in such a manner that they will be equally spaced within each cycle regardless if the number of groups selected per bank is changed or the number of banks is varied.

In present nuclear reactors this flexibility is not possible. Present plants required fixed number of banks with a fixed number of groups per bank. For example, it is common in present nuclear control plants to provide two banks with four groups each. It can be seen that such an arrangement is very inflexible and cannot meet the changing demands brought about by the varying requirements of energy from todays nuclear reactor.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel system to cyclically provide operation controlling pulse signals to groups of elements within a plurality of banks, where the number of banks and/or the number of groups per bank may be varied.

Another object of the present invention is to provide an improved pulse providing system which is both flexible and reliable.

Another object of the present invention is to provide an improved system for providing pulse signals for better withdrawing and inserting groups of control rods within a nuclear reactor.

Another object of the present invention is to provide an improved cyclical sequence of pulses in either the forward or reverse direction which are equally spaced within each cycle regardless of the number of pulses per cycle.

In accordance with the present invention, a reversible counter is provided for counting pulses provided by a pulse generator. The counter counts in the forward or reverse direction depending upon the desired direction of the sequencing cycle. Decoding means provide a plurality of element control pulses which are so spaced in time that it is possible to select from among the element control pulses equally spaced pulses per cycle regardless of the number of elements or groups of elements per bank. Once the number of elements per bank is determined, selected element control pulses may then be used for gating banks provided according to the particular bank or banks to be sequenced. The output, then, from the gating means is a cyclical sequence of equally spaced pulses in the derived direction to the elements comprising the bank or banks to be sequenced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the relationship between the output and internal signals from the novel system illustrated in FIG. 2;

FIG. 2 illustrates a system embodying the present invention;

FIG. 3 illustrates one embodiment of one subsystem shown in FIG. 2;

FIG. 4 illustrates another embodiment of one subsystem shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A, B and C of FIG. 1 illustrate the requirements of a pulse providing system to cyclically sequence of a plurality of elements, wherein the maximum number of elements or groups of elements per bank is three, i.e., where N 3. N may be any reasonable number in practice. The number three has been selected for purposes of illustration only and it should be understood that the present invention should not be so limited. In A of FIG. 1, N is equal to one element per bank. Thus in every cycle it is necessary to provide one control pulse at the indicated time per cycle. In the case of a nuclear rod control system the element 1 would comprise a first group of control rods, or more particularly one group of well known jack mechanisms for controlling and withdrawing a first plurality of reactor control rods. One such jack mechanism is disclosed in US Pat. No. 3,158,766 by E. Frisch. Further, a brief description of the operation of such a jack mechanism is given in patent application Ser. No. 798,912 (Westinghouse case 40,535). In B of FIG. 1, N is equal to two elements per bank. The indicated pulses are equally spaced in time within each cycle. In C of FIG. 1, N is equal to three or N Note again, that the pulses which must be provided are equally spaced within each cycle.

In FIG. 2 a preferred embodiment of the present invention is shown for providing the various pulse sequences shown in A, B and C of FIG. 1. A pulse generator 10 provides a pulse train characterized by having a number of pulses per cycle equal to the least common multiple of the factors comprising N,,,,,,!, where N is the maximum number of groups per bank and wherein the least common multiple of the factors comprising N is defined as the smallest number in which each of the factors of N may be divided into. For example if N is equal to five, N is equal to 54321. The smallest number into which each of the factors comprising 5!, that is, 5 4, 3, 2 and 1, is 60 and is defined as the lease common multiple. The number of pulses per cycle for N 3 is equal to six, i.e., the least common multiple of 3! is six, as shown in D of FIG. 1.

The output 11 from the pulse generator is then sent to one input of OR gate 12. The output from the OR gate is divided into two outputs l4 and 16 which are sent to AND gates 18 and 20 respectively to gate steady state input signals 22 and 24 provided at AND gates 18 and 20 respectively. A reversible counter is responsive to the output 26 of AND gate 18 or the output 28 of AND gate 20 for counting in the forward or reverse direction, respectively. Thus, input signal 22 when applied to AND gate 18 causes counter 30 to count in the forward direction. Similarly, an input signal 24 causes the counter 30 to count in the reverse direction. If the present invention is embodied in a nuclear rod control system, when it is desired to withdraw the control rods input signal 22 is provided at AND gate 18 and when it is desired to insert the rods an input signal 24 provided at the input 24 of AND gate 20.

Reversible counter 30 may be any standard reversible counter presently well known and used. It must have a capacity equal to the least common multiple of the factors comprising N L When counting in the forward direction, the counter must be capable of counting up to this number and then repeat itself. When counting in the reverse direction, it must be capable of counting down to and then cycle back up to the highest value and count back toward 0 again.

The outputs from the reversible counter 30 are shown in E of FIG. 1 where N 3, for outputs 32, 34 and 36 when the counter is operating in the forward direction. The output signal from each of the outputs 32, 34 and 36 can be either a binary 0 or 1 and collectively form the binary numbers as shown. The decoding means 40 is responsive to the outputs from the reversible counter to provide a plurality of element control pulses such that any number N up to N elements per bank may be selected among the element control pulses and be equally spaced in time. The decoder, which comprises a series of logic gates may be constructed according to well known techniques for digital logic decoder circuit design.

In the embodiment shown, N is 3. The counter capacity is six which is the least common multiple of 3!. The decoder accordingly provides four element control pulses P0, P2, P3 and P4 shown in F of FIG. 1, during the O, 2, 3 and 4 output states of the counter 30. These particular element control pulses are required so that all possible numbers up to N can be equally spaced within a cycle as illustrated in A, B and C of FIG. 1. Thus, pulse P0 is provided just before the counter switches from a binary 000 to a binary 001 since a pulse is received for N l, 2 or 3. When the counter changes states from 001 to 010 no element pulse is provided since, as seen in A, B and C of FIG. 1 no element would be required since it would be impossible to provide evenly spaced pulses within the cycle. However, when the counter changes from state 010 to 01 l a pulse must be provided where N N 3. Hence pulse P2 is outputed from the decoder 40. When the counter changes states from 01 l to 100 a pulse is required where N 2 as shown in B of FIG. 1. When the counter changes from 100 to 101 a pulse is required where N 3. When the counter changes from 101 to 000 it can be seen that no pulses are required.

This particular embodiment has been illustrated for N 3. The selection of the output pulses from the decoder will of course vary depending upon the value of N Further, E and F of FIG. 1 are representative of a counter operating in the forward direction. If the system is going in the reverse direction, the counter would change state just at the conclusion of each pulse from pulse generator 10. And, of course, the corresponding element pulses would be given just prior to each counter change.

Referring again to FIG. 2 the pulses P0, P2, P3 and P4, are then sent to a bank selector or matrix 42. Bank signal means 44, which is described and forms a basis of the above mentioned and related copending patent application Ser. No. 798,914, (W.E. case 40,741) provides a separate steady state signal to the bank selector 42 as to which banks of elements are to be sequenced.

One illustrative embodiment 42', of the bank selector 42 is shown in FIG. 3. Again, N is equal to 3, the number of groups N per'bank equal to 2, and the number of banks equal to 4. The pulses P0, P2, P3 and P4 from the decoder 40 are sent to a plurality or matrix of terminals, with terminals 46 being connectable with the decoder output providing element pulses P0, terminals 48 to the output of decoder 40 providing element pulses P2, terminals 50 to the output of the decoder providing element pulses P3, and the terminals 52 to the output providing element pulses P4. Similarly, the bank signals corresponding in number to the number of banks of elements, i.e., four, are sent to a second plurality or matrix of terminals. Terminals 54 are connected with the bank signal means 44 to receive the bank one signal. Similarly, terminals 56 receive bank two signal, terminals 58 bank three signal, and terminals 60 bank four signal.

The bank signals are then gated by selected signals P0 and P3. This is accomplished by connecting terminals appropriately selected from the bank terminal matrix to each of a plurality of AND gates. Element pulse terminals are connected with each of the AND gates thereby providing a means of gating the bank signals.

More particularly, line 62 is connected between terminals 64 and AND gate 66, line 68 is connected between terminal 70 and the AND gate 66, line 72 is connected between terminal 74 and AND gate 76, and line is connected between the AND gate 76, and terminal 78.

In operation, when it is desired to cyclically pulse the elements within the first bank, element pulses from the decoder, P0 and P3, will gate the signal from the bank signal means. If the direction of sequencing is in the forward direction, pulse P0 is transmitted from terminal 70 to the AND gate 66. When it does, the first bank signal at terminal 64, which is a continuous signal and which is present due to the determination that the bank one elements are to be pulsed, is gated by pulse P0 and hence a pulse is provided at the output of the AND gate 66 to pulse the first element in bank one. At the end of the pulse P0 no signal will be provided from AND gate 66. At the arrival of P3 at terminal 78 the first bank signal provided at 74 is gated at AND gate 76 to provide a pulse for the second element in bank one. Bank signals from the other banks are connected to other AND gates and gated by element pulses P0 and P3 in an identical manner. For bank 2, line 82 is connected between terminal 84 and AND gate 86 and line 88 is connected between terminal 90 and AND gate 86. Line 92 is connected between terminal 94 and AND gate 96 and line 98 between terminal 100 and AND gate 96. For bank 3, line 102 is connected between terminal 104 and AND gate 106 and line 108 between terminal 110 and AND gate 106. Line 112 is connected between terminal 114 and AND gate 116 and line 118 between terminal 120 and AND gate 116. For bank four, line 122 is connected between terminal 124 and AND gate 126 and line 128 between terminal 130 and AND gate 126. Line 130 is connected between terminal 132 and AND gate 134 and line 136 between terminal 138 and AND gate 134.

Any bank of elements may be sequenced merely by providing the desired bank signals. Since N in this example is three and since the number of elements N per bank is only two, additional AND gates and terminals are not used. Thus the AND gates 140, 142, 144 and 146 are not required where only two elements are utilized per bank. However should it be decided that one element per bank or three elements per bank would be desirable, then all that would be required would be a series of reconnections between the terminals from the decoder 40 and the AND gates. Utilization of more or less AND gates would depend upon whether three, two or one elements per bank were desired. For example, if only one element per bank were to be pulsed then only AND gates 66, 86, 106 and 126 would be needed and the remaining AND gates would be disconnected from their corresponding terminals.

A bank selector 42" where N 3 and where the number of elements per bank is also equal to three is illustrated in FIG. 4, for a system including typical number used in a nuclear rod control system. Banks C1, C2, C3 and C4 would correspond to ordinary control banks and banks S1 and S2 are shutdown banks and perform special functions within a nuclear reactor. However for purposes of this discussion all the banks perform in exactly the same manner and have the same sequential pulse requirements. The same element pulses, P0, P2, P3 and P4, from the decoder are provided since N is equal to three. In a nuclear reactor more than one control bank may never be withdrawn or inserted at the same time. To utilize the equipment more effectively, multiplexing of the power units to drive the control rods may be employed. Such a system is described in the copending patent application Ser. No. 798,914 (W.E. case 40,741). Since some of the banks are pulsed at the same time additional circuitry may be provided in the gating scheme to reduce the number of elements therein. H V V V g I In the embodiment shown in FIG. 4, control banks C1 and C3 and shutdown bank S1 are never operated or cyclically pulsed at the same time. Also, control banks C2 and C4 and shutdown bank S2 are never pulsed at the same time. The same terminal arrangement is provided for the element pulses from the decoder 40 as used in the embodiment in FIG. 3. Thus terminals 46, 48, 50 and 52 are connected to the respective outputs of the decoder 40. Since there are six banks of elements, there are six groups of terminals 148, 149, 150, 151, 152 and 153. Since, only one from among banks C1, C3 and S1 will ever be pulsed at any giventime OR gates 154, 155, 156 are utilized for each of the element pulses for those banks. More particularly, the outputs from three AND gates 156, 158 and 159 are provided to OR gate 154. AND gate 157 is provided with two inputs, one by a connection from a C1 bank terminal 148 and one from a P0 element pulse terminal 46 as shown. AND gate 158 is connected with a C3 bank terminal 150 and AND gate 159 is connected with an S1 bank terminal 152. A connection to each of these AND gates is made from a P0 element pulse terminal 46. The output from OR gate 154 will be provided whenever a bank signal is set for banks C1, C3 or S1 and will be for the first group or rods within the selected bank.

The output pulse from OR gate 155 will be sent to the second group of rods for either banks C1, C3 or S1. Hence connections are made from P2 element terminal 48' and the inputs of each of AND gates 160, 161 and 162. Other connections are made between a C1 bank terminal 148 and AND gate 160, between a C3 bank terminal 150 and AND gate 161, and between a S1 bank terminal 152 and AND gate 162. The output from AND gates 160, 161 and 162 inputed to OR gate 155. Again, the OR gate will provide an output pulse whenever any of the bank signals for banks C1, C3 and S1 are provided and upon the occurrence of a P2 element pulse.

The output pulse from OR gate 156 will be sent to the third and final group of rods for either banks C1, C3 or S1. An input of each of the AND gates 163, 164 and 165 are connected with P4 element terminal 52. The other input of AND gate 163 is connected to C1 bank terminal 148, AND gate 164 to C3 bank terminal 150, and AND gate 165 to S1 bank terminal 152.

Since, only one from among banks C2, C4 and S2 will ever be pulsed at one time an arrangement is provided similar to that for banks C1, C3 and S1. Here the output from OR gate 166 is used to pulse the first group of control rods in either banks C2, C4 or S2, the output from OR gate 167 to pulse the second group, and the output from 168 to pulse the third group.

Inputs to OR gate 166 are provided from AND gates 170, 171 and 172, each of which has one input connected to a P0 element pulse terminal 46 and also second inputs connected to a C2 terminal 149, a C4 terminal 151, and an S2 terminal 153, respectively. Inputs to OR gate 167 are provided from AND gates 173, 174, and 175, each of which has an input connected to a P2 element pulse terminal 48, and also second in puts connected to a C2 terminal 149, and C4 terminal 151 and an S2 terminal 153, respectively. Inputs to OR gate 168 are provided from AND gates 176, 177 and 178, each of which has one input connected to a P4 element pulse terminal 52' and also second inputs connected to a C2 terminal 149, a C4 terminal 151 and an S2 terminal 153, respectively. The outputs from the OR gates are shown as outputs 154, 156', 166,167 and 168' in FIG. 2.

If it were desirous to alter the number of elements or groups per bank this can be done easily by rearranging the connections between the element pulse terminals, the bank signal terminals, and the AND gates according to the number of elements or groups per bank which is desired. It should be noted that the number of elements or groups of elements per bank may be varied. Thus, in a rod control system, one bank might comprise two groups of rods and another three.

If the present system was previously shut down and stopped by removing inputs 22 and 24 from AND gates 18 and 20, respectively, after, for example, a P3 element pulse and it is desired to restart the system and if an input signal 22 or 24 is therefore provided, it can be seen that it may be necessary to await a passage of time of up to three counts.

The cycling speed may be increased by increasing the frequencing of the output pulses from pulse generator 10. However, in order to reduce the amount of time required to obtain the first output pulse from the bank selector 42 when a sequencing is first required or when a change in direction of the system is called for, a fast pulse generator 180 provides a train of pulses at a much higher frequency than that from the pulse generator 10. The output 181 from the fast pulse generator 180 is sent and gated with the output from pulse generator 10; then to OR gate 12 to the AND gates 18 and 20, and to reversible counter 30. Thus, when the system changes direction or is first started by application of either input signal 22 or 24, a signal is also provided at the input 182 of the fast pulse generator. This results in a much faster count by the counter 30 and an increase response time for the issuance of element pulses from the decoder 40 and a first output pulse from the bank selector 42.

It is necessary to stop the effect of the fast pulse generator 180 as soon as the first pulse is provided by the bank selector 42 so that subsequent pulses will be spaced properly. Lines 184 are connected to the outputs of the bank selector 42, i.e., to the outputs of OR gates 154, 155, 156, 166, 167 and 168 (FIG. 4), and connected to OR gate 186. The output from the OR gate 186, which will be provided whenever the first pulse is provided from any of the bank selector 42 inputs, is sent to the fast pulse generator along line 188 to inhibit the fast pulse generator 180.

For proper operation of the system, it is a requirement that the last element pulses given while in a forward cycle must be the first given when a change of direction is desired. Similarly, the last pulse given in the reverse direction before a change of direction must also be the first given when the forward direction is given. This requirement is particularly important in a rod control system. There, the last group of rods withdrawn, must, for example, be the first inserted. If not rod misalignment resulting in reactor inefficiencies will result.

Decoder 40, as noted previously, provides element pulses only at the instant before a change in counter state. Taking the situation where the number elements per bank is equal to N,,,,, 3, and wherein the system is moving in a forward direction, an element pulse P0 is provided just as the counter changes from state zero to state one. Similarly, an element pulse P2 is provided as the counter changes from state two to state three and element pulse P3 is provided when the counter changes from state three to state four (although it is not utilized with a number of three groups per bank). At this point, if the sequencing direction is reversed or if the forward sequencing is first halted and then reversed, the decoder would provide pulse P4 since the decoder, as noted earlier, always provides an element pulse before it changes state. It can be seen that pulse P4 is erroneous because, in the case of a nuclear reactor for example, it will result in a reverse pulse to the third group of rods rather than to the last forward pulsed group, i.e.,

group 2 rods. Erroneous pulses will also be given when a change is made from the reverse to forward directions. No erroneous pulses are given if the sequence is halted and then continued in the same direction.

Means for eliminating the first element pulse signal following a change of direction is therefore provided to eliminate this problem. A first pulse control 190 has two input terminals 192 and 194 connected to the outputs of the AND gates 18 and 20. The output from the first pulse control 190 normally is used as a strobe signal 191 for synchronizing the element pulse outputs from decoder 40. But, whenever a change in cycling direction is ordered an input signal will be provided either at terminal 192 or 194 and removed from either terminal 194 or 192 respectively of first pulse control 190. When either of these events occurs first pulse control 190 inhibits the strobe signal 191 to prevent the issuance of the first element pulse following the change in direction. The first pulse control 190 is only operable to inhibit strobe signal 191 where a change in direction is called for and would not be applicable, for example if the system going in a forward direction, stopped, and then ordered to continue in the forward direction again. First pulse control 190 comprises a series of logic elements and may easily be constructed by one skilled in the art of logical digital design.

In the above examples N was selected equal to 3. It should be realized, however, that N may be any number so long as the pulse generator provides a number of pulses and so long as the counter capacity is equal to the least common multiples of the factors comprising N While there has been shown or described what are at present considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangements shown and described and it is intended to cover all such modifications as fall within the true spirit and scope of the invention.

1 claim as my invention: 1. A system for providing cyclical pulse control signals in a selected one of a forward or reverse sequence to elements within a plurality of banks comprising from one to N elements, and wherein the pulse signals are equally spaced in time for a given cycle period regardless of the number of elements per bank, comprising;

first pulse signal generating means for providing a pulse train having a pulse rate per cycle equal to the least common multiple of the factors comprising N,,,,,,

signal counting means having capacity at least equal to the least common multiple of the factors comprising N for accumulating the pulses from said pulse signal generating means in one of a forward or reverse sequence;

means operable to cause said counter to count in either the forward or in the reverse sequence in accordance with the desired cycling direction;

decoding means responsive to the state of said counting means operable to provide a cyclical sequence of element pulses from a corresponding number of outputs such that any number of the element pulses up to N may be equally spaced during one counter cycle;

bank signal means for providing bank signals in accordance with the desired banks to be sequenced;

means for gating the bank signals in response to equally spaced element pulses selected according to the number of elements per bank to provide equally spaced cylical output pulses signals to the elements within the desired banks.

2. A system as in claim 1 including means for decreasing the response time required to provide the first output pulse comprising:

second pulse signal generating means for providing a pulse train signal having a frequency greater than that of said first pulse generating means to said reversible counting means; means for inhibiting said first pulse signal generating means in response to the first provided cyclical pulse.

3. A system as in claim 1 wherein the means for gating the bank signals comprises:

A first plurality of terminals connected to the outputs of said decoding means operable to receive the element pulses;

a second plurality of terminals connected to receive bank signals from said bank signal means;

a plurality of gate means;

means for selectively connecting said first and second pluralities of terminals with said plurality of gate means in accordance with the number of banks and number of elements per bank, such that the elements within each bank will be cyclically pulsed with equally spaced pulses whenever a corresponding bank signal is provided and gated by the element pulses.

4. A system as in claim 1, wherein two or more banks of elements are not pulsed coincidentally, comprising:

a first plurality of terminals connected to the outputs of said decoding means operable to receive the element pulses;

a second plurality of terminals connected to receive bank signals from said bank signal means;

a plurality of gate means;

means for selectively connecting said first and second pluralities of terminals with said plurality of gate means in accordance with the number of banks and number of elements per bank such that only one bank among a plurality of banks will be cyclically pulsed with equally spaced pulses whenever a corresponding bank signal is provided and gated by the element pulses.

5. A system as in claim 1, including means for suppressing the first element subsequent to a change in cycling direction so that the last element provided prior to the change of direction will be provided after the change of direction.

6. In a nuclear reactor rod control system, including a plurality of banks of control rods, wherein each bank comprises one or more groups of control rods, and each rod may be incrementally withdrawn or inserted by a mechanism, apparatus for providing a sequence of control signals to sequentially energize each of said mechanisms within a group, comprising a. means for providing a sequence of pulse signals operable to energize any number of groups of control rod mechanisms per bank;

b. means for selecting pulse signals according to the number of groups per bank to be sequentially energized;

c. means for providing a sequence of control signals to drive groups of mechanisms according to the pulse signals selected. 

1. A system for providing cyclical pulse control signals in a selected one of a forward or reverse sequence to elements within a plurality of banks comprising from one to Nmax elements, and wherein the pulse signals are equally spaced in time for a given cycle period regardless of the number of elements per bank, comprising; first pulse signal generating means for providing a pulse train having a pulse rate per cycle equal to the least common multiple of the factors comprising Nmax!; signal counting means having capacity at least equal to the least common multiple of the factors comprising Nmax! for accumulating the pulses from said pulse signal generating means in one of a forward or reverse sequence; means operable to cause said counter to count in either the forward or in the reverse sequence in accordance with the desired cycling direction; decoding means responsive to the state of said counting means operable to provide a cyclical sequence of element pulses from a corresponding number of outputs such that any number of the element pulses up to Nmax may be equally spaced during one counter cycle; bank signal means for providing bank signals in accordance with the desired banks to be sequenced; means for gating the bank signals in response to equally spaced element pulses selected according to the number of elements per bank to provide equally spaced cylical output pulses signals to the elements within the desired banks.
 2. A system as in claim 1 including means for decreasing the response time required to provide the first output pulse comprising: second pulse signal generating means for providing a pulse train signal having a frequency greater than that of said first pulse generating means to said reversible counting means; means for inhibiting said first pulse signal generating means in response to the first provided cyclical pulse.
 3. A system as in claim 1 wherein the means for gating the bank signals comprises: A first plurality of terminals connected to the outputs of said decoding means operable to receive the element pulses; a secOnd plurality of terminals connected to receive bank signals from said bank signal means; a plurality of gate means; means for selectively connecting said first and second pluralities of terminals with said plurality of gate means in accordance with the number of banks and number of elements per bank, such that the elements within each bank will be cyclically pulsed with equally spaced pulses whenever a corresponding bank signal is provided and gated by the element pulses.
 4. A system as in claim 1, wherein two or more banks of elements are not pulsed coincidentally, comprising: a first plurality of terminals connected to the outputs of said decoding means operable to receive the element pulses; a second plurality of terminals connected to receive bank signals from said bank signal means; a plurality of gate means; means for selectively connecting said first and second pluralities of terminals with said plurality of gate means in accordance with the number of banks and number of elements per bank such that only one bank among a plurality of banks will be cyclically pulsed with equally spaced pulses whenever a corresponding bank signal is provided and gated by the element pulses.
 5. A system as in claim 1, including means for suppressing the first element subsequent to a change in cycling direction so that the last element provided prior to the change of direction will be provided after the change of direction.
 6. In a nuclear reactor rod control system, including a plurality of banks of control rods, wherein each bank comprises one or more groups of control rods, and each rod may be incrementally withdrawn or inserted by a mechanism, apparatus for providing a sequence of control signals to sequentially energize each of said mechanisms within a group, comprising a. means for providing a sequence of pulse signals operable to energize any number of groups of control rod mechanisms per bank; b. means for selecting pulse signals according to the number of groups per bank to be sequentially energized; c. means for providing a sequence of control signals to drive groups of mechanisms according to the pulse signals selected. 